The real difference between the RDL and SLDL is bar position.
Originally Posted by Eric3237
That's right. Romanian's keep the bar close in and you stick your butt out. Regualar SLDL's the bar is out further in front of you.
At least that is the way I understand it.
During the RDL, the hips move backward, thus keeping the bar close to the body. However, during the SLDL, the butt stays somewhat put (it will move back slightly). You'll still rotate around the hips, but the bar is now further away from the body.20 This, of course, will place greater stress on the lumbar erectors (your lower back.)17
Overall, there's less stress on the low back and greater weight can be used with the RDL since the load is closer to the axis of rotation and over the base of support.3 For this reason, you can go pretty heavy with RDL's as long as you maintain strict form.
3. Ballantyne, CS. The Deadlift: 1 Exercise, 18 Variations. Issue #75. http://www.cbathletics.com
17. Piper, TJ, Waller, MA. Variations of the Deadlift. Strength and Conditioning Journal, 2001, Vol. 23, No. 3, pp. 66ó73.
20. Tsatsouline, P. Full Range of Motion or Joint's Demolition Project?
Authored by: John Paul Catanzaro, B.Sc., C.K., P.F.L.C.
The Romanian Deadlift (RDL) is used primarily to strengthen the hamstrings, gluteus, and lower back, although this technique causes less stress to the lumbar area. Unlike the SLDL, the RDL is initiated from the floor, although the set up is roughly in-between that of the conventional deadlift and the SLDL. (23) During the ascension, the knees should begin to straighten in advance of the hips, with the goal of keep the torso at the same angle as in the beginning of the lift for as long as possible. This should occur while maintaining normal spinal curvature. Pulling in such a manner allows the athlete to keep the bar closer to the base of support, decreasing the strain on the lumbar area when compared to the SLDL. As the knees fully straighten, the hips shall travel toward the rear slightly, then the hips are then powerfully flexed, fully utilizing the hamstrings and erectors to complete the lift.
23. Whaley, O., and McClure, R. Another perspective on teaching the pulling movements. Strength Cond. J. 19:58-61. 1997.
IMO, RDLís are a great hip extensor exercise. The hip extensors are the muscle groups that act to extend the hip which are primarily the hamstrings and the glutes.